Hadn't given this a second thought. Don't all pickups have part-time transfer cases with dog gears, synchros, and shift levers that engage the front axle locked to the rear and optionally engage a planetary gearset for additional gear reduction? Apparently not!
Researching this has been difficult with lots of different technologies, minimal stuff easily found on the Internet and lots of somewhat conflicting stories. On top of that, there have been changes in the ownership of the transfer case manufacturers.
Let's stay with the BorgWarner cases on the DS and DT Ram 1500s, the 44-44/44-45, and 48-11/48-12. The 48-13 is a version on the TRX.
BW uses a chain to connect the input shaft to the front output shaft. This is common and BW uses the chain to distribute oil throughout the transfer case.
I always thought the part-time transfer cases used dog gears to engage the front axle. It is either mechanically locked or not.
BW uses a multi-disc clutch back to engage 4wd. I'm still trying to get a handle on this as it seems very similar to the Haldex AWD drive used on VW and some Audi models. Haldex is also owned by BW however I believe BW was using a multi-disc wet clutch before they bought Haldex. The discs in the video are hydraulically engaged as shown around 2:10 in the video below although I believe the Ram versions are all electromagnetic. the plate applying the pressure having ramps on 3 balls that press the disks together as the plate rotates.
This is a video of the BW box from a 4WD perspective:
However, it gets more interesting. This video shows a ram with a BW 48-11 in various settings. Note that the system is always starting open, even in 4Hi and 4Lo, and then decides to lock or come close to locking. This can be an issue in some situations where the driver relies on everything being locked for control. This would be most apparent where the driver is moving slowly with minimal and varying throttle. In the video below it is always on a relatively firm surface with a significant throttle application.
That video should be showing the 48-11 which like the 44-44 has the variable pressure on clutch engagement. There was a kit for the 44-44 to cause it to lock and not do the partially locked dance. There are reports of people using their trucks for snow plowing or use on the beach or other sandy surfaces who had failures with the 44-44 and some who converted to a 44-45. Haven't found any posts on the 48-11/12.
www.transmissiondigest.com
Then apparently one of the configurations for the 44-44 and presumably the 48-11 is the tire size. From the documentation, I read the only sizes available are OEM and can't be changed other than to another OEM size. People are changing tire sizes all the time, so is that setting useless?
The mechanism is apparently also very sensitive to differences in tire diameter and a 1/4" difference in circumference. That could occur from mismatched tire pressures, a different size tire (must the spare be used only in 2Hi?), or even different tire wear (1/4" in circumferences is only 1mm, less than 1.5/32nds of an inch, in treadwear).
www.transmissiondigest.com
www.transmissiondigest.com
So...I'm confused. Is it really hyper-sensitive to differences in tire-loaded radius? Is it subject to high wear in uses where it has slippage under high load/low traction surfaces? Does it not really lock possibly causing issues in some circumstances?
BorgWarner has been making a version of these transfer cases for over 15 years so presumably, they know what they want. Do they?
Note the Jeep Wrangler uses a Magna (Magna bought New Venture which was a GM/Chrysler program for New Process) box for many of its applications with the auto mode that uses similar wet clutches but has different programming. Haven't seen a comparison of the two.
Researching this has been difficult with lots of different technologies, minimal stuff easily found on the Internet and lots of somewhat conflicting stories. On top of that, there have been changes in the ownership of the transfer case manufacturers.
Let's stay with the BorgWarner cases on the DS and DT Ram 1500s, the 44-44/44-45, and 48-11/48-12. The 48-13 is a version on the TRX.
BW uses a chain to connect the input shaft to the front output shaft. This is common and BW uses the chain to distribute oil throughout the transfer case.
I always thought the part-time transfer cases used dog gears to engage the front axle. It is either mechanically locked or not.
BW uses a multi-disc clutch back to engage 4wd. I'm still trying to get a handle on this as it seems very similar to the Haldex AWD drive used on VW and some Audi models. Haldex is also owned by BW however I believe BW was using a multi-disc wet clutch before they bought Haldex. The discs in the video are hydraulically engaged as shown around 2:10 in the video below although I believe the Ram versions are all electromagnetic. the plate applying the pressure having ramps on 3 balls that press the disks together as the plate rotates.
This is a video of the BW box from a 4WD perspective:
However, it gets more interesting. This video shows a ram with a BW 48-11 in various settings. Note that the system is always starting open, even in 4Hi and 4Lo, and then decides to lock or come close to locking. This can be an issue in some situations where the driver relies on everything being locked for control. This would be most apparent where the driver is moving slowly with minimal and varying throttle. In the video below it is always on a relatively firm surface with a significant throttle application.
That video should be showing the 48-11 which like the 44-44 has the variable pressure on clutch engagement. There was a kit for the 44-44 to cause it to lock and not do the partially locked dance. There are reports of people using their trucks for snow plowing or use on the beach or other sandy surfaces who had failures with the 44-44 and some who converted to a 44-45. Haven't found any posts on the 48-11/12.
Snow plowing = BW 44-44 transfer-case failures - Transmission Digest
Experience we gain from solving problems generated in the transmission repair industry sheds light on various common failures and allows us to see trends that provide new products to solve design issues. From 2011 on, Dodge has offered Ram 1500 pickup trucks equipped with the BW 44-44 transfer...
www.transmissiondigest.com
Then apparently one of the configurations for the 44-44 and presumably the 48-11 is the tire size. From the documentation, I read the only sizes available are OEM and can't be changed other than to another OEM size. People are changing tire sizes all the time, so is that setting useless?
The mechanism is apparently also very sensitive to differences in tire diameter and a 1/4" difference in circumference. That could occur from mismatched tire pressures, a different size tire (must the spare be used only in 2Hi?), or even different tire wear (1/4" in circumferences is only 1mm, less than 1.5/32nds of an inch, in treadwear).
Transfer Cases and Tires: How Ram is changing the rules - Transmission Digest
The design uses a wet-clutch pack in the transfer case to split torque between the rear and front axles.
www.transmissiondigest.com
BorgWarner 44-44 Transfer Case from the Electronic Side - Transmission Digest
Discover the inner workings of the BW 44-44 transfer case and its electronically controlled active full-time operation in Ram pickups.
www.transmissiondigest.com
So...I'm confused. Is it really hyper-sensitive to differences in tire-loaded radius? Is it subject to high wear in uses where it has slippage under high load/low traction surfaces? Does it not really lock possibly causing issues in some circumstances?
BorgWarner has been making a version of these transfer cases for over 15 years so presumably, they know what they want. Do they?
Note the Jeep Wrangler uses a Magna (Magna bought New Venture which was a GM/Chrysler program for New Process) box for many of its applications with the auto mode that uses similar wet clutches but has different programming. Haven't seen a comparison of the two.
